Dead reckoning measurements from inertial sensors improve satellite derived position and velocity estimates. A car navigation system that combines GNSS and inertial measurements, e.g. using Kalman filtering, can provide acceptable accuracy during GNSS signal reception outages, especially when map-matching techniques are used for vehicles assumed to travel on roads. (Global navigational satellite systems (GNSS) include the Global Positioning System (GPS), GLONASS, Beidou/Compass, and Galileo.)
For car navigation, yaw rate and wheel tachometer measurements may be used to propagate position and velocity estimates between GNSS fixes. However, for such systems to work well the axis of the yaw rate gyro must be aligned with the vertical axis of the vehicle it is mounted in; otherwise, accuracy suffers. Conventional systems are based on single-axis yaw rate gyros.
Even when advanced manufacturing techniques are employed, it is not always possible to specify the relevant mounting angles to a designer of dead reckoning modules. A module that is used in several different vehicle models, for example, may be mounted in a different orientation in each.
Hence, what is needed is a dead reckoning module for car navigation that can be mounted in various orientations without compromising the accuracy of gyro angular rate measurements.